The present invention relates to a thrust reverser for a turbofan-type turbojet engine in which pivotable thrust reverser doors change the direction of the flow of air passing through a cold-flow air duct to provide the necessary thrust reversing forces.
Turbofan-type turbojet engines are well known in the art and, typically, comprise an annular housing concentrically arranged around the turbojet engine housing to define an annular cold-flow air duct extending along the longitudinal axis of the engine. A fan, driven by the turbojet engine, is located in the upstream portion of the cold-flow air duct to force air through the duct and augment the thrust of the turbojet engine.
In such turbofan-type turbojet engines having a relatively high bypass ratio, a thrust reversing device may be associated with the annular housing to redirect the air passing through the cold-flow air duct to provide a thrust reversing force. It is known to provide one or more pivotable thrust reversing doors in the annular housing to redirect the cold-flow air through openings in the housing.
A typical prior art installation is illustrated in FIGS. 1 and 2 and comprises annular housing 1, a thrust reverser 2 and a downstream housing portion 3. The upstream housing portion 1 comprises an outer surface panel 4 and an inner surface panel 5 interconnected by a frame structure 6. Similarly, downstream housing portion 3 has an inner surface panel 3a and an outer surface panel 3b.
The thrust reverser 2 comprises a pivotable door 7 and an actuator 7a interconnecting the door 7 with the frame structure 6. The actuator 7a, which may be a hydraulic cylinder, is attached to the frame structure 6 and has an extendible and retractable rod attached to pivoting door 7.
The door 7 extends between upstream housing portion 1 and downstream housing portion 3 so as to normally cover a generally laterally facing opening defined by the housing when the turbofan engine operates in the forward thrust mode. In this mode, as illustrated in FIG. 1, the outer door panel 9 is substantially flush with the outer surface panel 4 and the outer downstream surface panel 3b to provide a smooth air flow (indicated by arrow 10) over the exterior of the housing.
The piston rod of the actuating cylinder 7a is connected to internal structure 12 of the thrust reverser door 7. Internal structure 12 interconnects the outer door panel 9 with the inner door panel 11, which panels are also connected at their upstream edges by baffle member 13.
In known fashion, extension of the piston rod of actuator 7a causes the door 7 to pivot with respect to the housing such that its upstream end portion swings outwardly while its downstream end portion swings inwardly to block off the air flow 15 flowing through the cold-flow air duct. The air is redirected by the door outwardly through the lateral opening in the annular housing to provide a thrust-reversing force. When the door is in the open, thrust-reversing position, deflection edge 8, extending from the inner housing panel 5, minimizes the turbulence of the air passing outwardly through the opening. Baffle member 13 imparts a forward vector to the air passing through the lateral opening to increase the efficiency of the door. In order to achieve the maximum efficiency, baffle member 13 must extend beyond the surface of the inner door panel 11.
When the door is in its closed position, as illustrated in FIG. 1, an internal cavity 16 is formed, bounded by the inner door panel 11, the extending portion of the baffle member 13, the deflection edge 8 and a theoretical air flow line 14 extending between the inner surface panel 5 and the inner surface 3a of the downstream housing portion 3. Line 14 represents the ideal theoretical air flow through the cold-flow air duct. The presence of cavity 16 causes disturbances in the air flow 15, thereby reducing the efficiency of the device in the forward thrust mode. When in this mode, seal member 17 contacts the inner side of outer door panel 9 to prevent entry of the ambient air.
Typical examples of such known thrust reversing systems may be found in U.S. Pat. Nos. 4,410,152 and 4,485,970 as well as French Patent 2,559,838.
Various systems have been proposed to eliminate the presence of cavity 16, while still maintaining the efficiency of the baffle member 13. Such systems have included movable baffle members, as well as inner door panels 11 which move relative the outer door panel 9 as the door is moved between the opened and closed positions. While these systems have achieved a modicum of success, they inherently result in a thrust reversing door system of undesired complexity. Typical examples of such systems may be found in U.S. Pat. No. 4,894,985 as well as U.S. Pat. No. 4,916,895.
It is imperative that the door 7 remain in its closed position and be deployed only when desired, during the landing and braking stages when the aircraft is on the ground. Known mechanical locking devices are provided to lock the door in the closed positions. However, it is desirable that the door 7 be maintained in its closed position even if the mechanical locking device should fail. The inadvertent opening of a thrust reverser door could result in the loss of control of the aircraft with consequent catastrophic results. In some known thrust reverser systems, such as that illustrated in U.S. Pat. No. 4,485,970 the air pressure forces acting on the pivoting door tend to urge the door into an opened position. This quite possibly could, upon failure of the mechanical locking device, cause an inadvertent opening of the thrust reverser door.